Stir together sour cream and brown sugar until the sugar is fully incorporated. Cover and refrigerate until ready to use.
Divide room-temperature raspberries among 4 pretty serving bowls or goblets. Top each serving with a dollop of the chilled crème cassonade.
Notes
Feel free to change the berries based on what is in season, and you can even play with the sweetener both honey and maple syrup work but they will change the colour of the cream slightly.